Found what it was. When I got it he had changed the oil. It started this right after I bought it with the wife cutting with it. It was last cutting of the year, so it just set until I had time to check it out . We only cut a small side yard with it because I can't get the 60 zero turn into the side yard. Where we keep it is on a slight tilt. When I check the oil, it showed to top mark. When I started it up she ran fine for about 5 minutes. When I engaged blade to cut she ran fine. When I turned around down hill she started smoking. So now, I go and check oil, she was about 2/3 of a quart high. (Level ground) I guess when I bought it she was setting on a tilt in his yard. She ran fine. Brought her home and rolled her off trailer with no problem. When wife went to cut, up hill was fine, down about half, she smoked. Drained out the oil and now she is fine. On by the way, she is an 18.5 hp, not a 17.5 hp. This one is on another mower.